The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Nonvolatile semiconductor memory retains data after power is removed and includes a memory array. Memory arrays that include NAND-type or NOR-type memory cells (e.g., NAND-type or NOR-type flash memory cells) are called NAND-type or NOR-type memory arrays, respectively. Memory arrays typically include memory cells arranged in rows and columns. Data is read from or written to the memory cells using decoder circuits (decoders) that select word lines (WLs) and bit lines (BLs) corresponding to the memory cells. Some memory cells store two or more bits of data. The multiple bits may be represented in the cell via multiple charged state levels.
A sense amplifier circuit for a nonvolatile memory array performs various functions. One function senses data that is stored in multi-level cells of the nonvolatile memory array. Another function temporarily stores the sensed data before outputting the sensed data to an input/output (I/O) circuit.
Another function temporarily stores input data, for example, from the I/O circuit until the input data can be stored in the nonvolatile memory array. Another function handles program, erase, and verify operations. The program operation writes data in a memory cell. The program operation may change the state of a memory cell to alter one or more bits stored in the memory cell. The erase operation removes data from a memory cell. The erase operation may reset the memory cell to a default state. The verify operation ensures that a memory cell is in a proper state after the program or erase operation.
The sense amplifier circuit may include current and/or voltage sensing circuits. For example only, during a read operation, the sense amplifier circuit detects data stored in a cell of the nonvolatile memory array. A wordline of the nonvolatile memory array is biased while data in the cell is sensed via one or more bit lines. Once the data is sensed, the data is passed to the I/O circuit. Bits of information that are stored in the cell are accessed one bit at a time for each corresponding processing cycle.